Process groups

package.json

@@ -55,7 +55,7 @@
     "@types/find-root": "^1.1.2",
     "@types/jest": "^27.4.0",
     "@types/lodash": "^4.14.194",
-    "@types/node": "^14.14.14",
+    "@types/node": "^18.11.9",
     "@types/yargs": "^15.0.14",
     "eslint": "^8.40.0",
     "eslint-plugin-jest": "^27.2.1",

spec/Supervisor.spec.ts

@@ -2,6 +2,8 @@ import { ChildProcess, spawn } from "child_process";
 import { range } from "lodash";
 import * as path from "path";
 
+jest.setTimeout(10000);
+
 const childExit = (child: ChildProcess) => {
   return new Promise<void>((resolve) => {
     child.on("exit", (code: number) => {
@@ -106,4 +108,4 @@ test("it doesn't have any stdin if wds is started with terminal commands", async
   await childExit(child);
 
   expect(output).toEqual("");
-});
+});

src/Project.ts

@@ -58,8 +58,8 @@ export class Project {
     this.supervisor.restart();
   }
 
-  shutdown(code = 0) {
-    this.supervisor.stop();
+  async shutdown(code = 0) {
+    await this.supervisor.stop();
     for (const cleanup of this.cleanups) {
       cleanup();
     }

src/Supervisor.ts

@@ -1,6 +1,7 @@
+import { setTimeout } from "timers/promises";
 import type { ChildProcess, StdioOptions } from "child_process";
 import { spawn } from "child_process";
-import { EventEmitter } from "events";
+import { EventEmitter, once } from "events";
 import type { RunOptions } from "./Options";
 import type { Project } from "./Project";
 import { log } from "./utils";
@@ -12,28 +13,41 @@ export class Supervisor extends EventEmitter {
     super();
   }
 
-  stop() {
-    if (this.process) {
-      this.process.kill("SIGTERM");
+  /**
+   * Stop the process with a graceful SIGTERM, then SIGKILL after a timeout
+   * Kills the whole process group so that any subprocesses of the process are also killed
+   * See https://azimi.me/2014/12/31/kill-child_process-node-js.html for more information
+   */
+  async stop() {
+    if (!this.process || !this.process.pid) return;
+
+    const ref = this.process;
+    const exit = once(ref, "exit");
+    this.kill("SIGTERM");
+
+    await Promise.race([exit, setTimeout(5000)]);
+    if (!ref.killed) {
+      this.kill("SIGKILL", ref.pid);
     }
-    const process = this.process;
-    setTimeout(() => {
-      if (!process.killed) {
-        process.kill("SIGKILL");
-      }
-    }, 5000);
   }
 
-  kill() {
-    if (this.process) {
-      this.process.kill("SIGKILL");
+  kill(signal = "SIGKILL", pid = this.process?.pid) {
+    if (pid) {
+      try {
+        process.kill(-pid, signal);
+      } catch (error: any) {
+        if (error.code == "ESRCH") {
+          // process can't be found, is already dead
+          return;
+        } else {
+          throw error;
+        }
+      }
     }
   }
 
   restart() {
-    if (this.process) {
-      this.process.kill("SIGKILL");
-    }
+    this.kill();
 
     const stdio: StdioOptions = [null, "inherit", "inherit"];
     if (!this.options.terminalCommands) {
@@ -51,6 +65,7 @@ export class Supervisor extends EventEmitter {
         WDS_EXTENSIONS: this.project.config.extensions.join(","),
       },
       stdio: stdio,
+      detached: true,
     });
 
     if (this.options.terminalCommands) {

src/index.ts

@@ -156,11 +156,11 @@ export const wds = async (options: RunOptions) => {
 
   process.on("SIGINT", () => {
     log.debug(`process ${process.pid} got SIGINT`);
-    project.shutdown(0);
+    void project.shutdown(0);
   });
   process.on("SIGTERM", () => {
     log.debug(`process ${process.pid} got SIGTERM`);
-    project.shutdown(0);
+    void project.shutdown(0);
   });
 
   project.supervisor.process.on("exit", (code) => {
@@ -172,7 +172,7 @@ export const wds = async (options: RunOptions) => {
       return;
     }
     logShutdown("shutting down project since it's no longer needed...");
-    project.shutdown(code ?? 1);
+    void project.shutdown(code ?? 1);
   });
 
   return server;